Technical description of the forecast

The energy weather forecast converts sunshine and wind into kilowatt hours for each location over the next 24 hours.

Produced in the BCDC Energy research project, the energy weather forecast assumes a peak power of 2.5 kWp for solar panels and wind turbines. Therefore, the wind and solar power production figures of the forecast are comparable with one another.

The forecast is based on the HIRLAM weather forecast model of the Finnish Meteorological Institute. HIRLAM includes all weather-related details significant for both wind and solar power. More information about weather forecast models is available here: What are weather forecast models? (in Finnish) Weather forecast models help to make accurate weather forecasts (in Finnish)

For solar power, the energy weather forecast includes an assumption of a 2.5 kWp panel which is facing the south and has been installed at a 30-degree angle from the horizontal level. This corresponds to a small solar panel installed on the roof of a detached house. On the basis of information provided by the weather forecast model, the energy weather forecast first estimates the amount of solar irradiance on the specific inclined surface. Because the efficiency ratio of solar panels depends on their temperature, the efficiency ratio in the current weather conditions is next calculated on the basis of irradiance, temperature and weather information. By combining these, the forecast estimates the expected solar power production.

For wind power, the energy weather forecast includes an assumption of a wind turbine with a hub height of 12 metres suitable for small-scale wind power production. The wind power forecast is produced by combining the wind speed at a height of 10 metres provided by the weather forecast model with the power curve of the specific wind turbine.

kWh = kilowatt hour
kWp = kilowatt, peak (Absolute peak power without any disturbance, particulates, clouds or moisture; the actual calculation takes such disturbances into account.)

What does the kilowatt hour mean in practice?

Power companies offer lists that clearly indicate how much energy household appliances consume in kilowatt hours, e.g.